Changes in environmental exposures over decades may influence the genetic architecture of severe spermatogenic failure

STUDY QUESTION

Do the genetic determinants of idiopathic severe spermatogenic failure (SPGF) differ between generations?

SUMMARY ANSWER

Our data support that the genetic component of idiopathic SPGF is impacted by dynamic changes in environmental exposures over decades.

WHAT IS KNOWN ALREADY

The idiopathic form of SPGF has a multifactorial etiology wherein an interaction between genetic, epigenetic, and environmental factors leads to the disease onset and progression. At the genetic level, genome-wide association studies (GWASs) allow the analysis of millions of genetic variants across the genome in a hypothesis-free manner, as a valuable tool for identifying susceptibility risk loci. However, little is known about the specific role of non-genetic factors and their influence on the genetic determinants in this type of conditions.

STUDY DESIGN, SIZE, DURATION

Case-control genetic association analyses were performed including a total of 912 SPGF cases and 1360 unaffected controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All participants had European ancestry (Iberian and German). SPGF cases were diagnosed during the last decade either with idiopathic non-obstructive azoospermia (n = 547) or with idiopathic non-obstructive oligozoospermia (n = 365). Case-control genetic association analyses were performed by logistic regression models considering the generation as a covariate and by in silico functional characterization of the susceptibility genomic regions.

MAIN RESULTS AND THE ROLE OF CHANCE

This analysis revealed 13 novel genetic association signals with SPGF, with eight of them being independent. The observed associations were mostly explained by the interaction between each lead variant and the age-group. Additionally, we established links between these loci and diverse non-genetic factors, such as toxic or dietary habits, respiratory disorders, and autoimmune diseases, which might potentially influence the genetic architecture of idiopathic SPGF.

LARGE SCALE DATA

GWAS data are available from the authors upon reasonable request.

LIMITATIONS, REASONS FOR CAUTION

Additional independent studies involving large cohorts in ethnically diverse populations are warranted to confirm our findings.

WIDER IMPLICATIONS OF THE FINDINGS

Overall, this study proposes an innovative strategy to achieve a more precise understanding of conditions such as SPGF by considering the interactions between a variable exposome through different generations and genetic predisposition to complex diseases.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the "Plan Andaluz de Investigación, Desarrollo e Innovación (PAIDI 2020)" (ref. PY20_00212, P20_00583), the Spanish Ministry of Economy and Competitiveness through the Spanish National Plan for Scientific and Technical Research and Innovation (ref. PID2020-120157RB-I00 funded by MCIN/ AEI/10.13039/501100011033), and the 'Proyectos I+D+i del Programa Operativo FEDER 2020' (ref. B-CTS-584-UGR20). ToxOmics-Centre for Toxicogenomics and Human Health, Genetics, Oncology and Human Toxicology, is also partially supported by the Portuguese Foundation for Science and Technology (Projects: UIDB/00009/2020; UIDP/00009/2020). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Molecular mechanisms of cellular dysfunction in testes from men with non-obstructive azoospermia

Male factor infertility affects 50% of infertile couples worldwide; the most severe form, non-obstructive azoospermia (NOA), affects 10-15% of infertile males. Treatment for individuals with NOA is limited to microsurgical sperm extraction paired with in vitro fertilization intracytoplasmic sperm injection. Unfortunately, spermatozoa are only retrieved in ~50% of patients, resulting in live birth rates of 21-46%. Regenerative therapies could provide a solution; however, understanding the cell-type-specific mechanisms of cellular dysfunction is a fundamental necessity to develop precision medicine strategies that could overcome these abnormalities and promote regeneration of spermatogenesis. A number of mechanisms of cellular dysfunction have been elucidated in NOA testicular cells. These mechanisms include abnormalities in both somatic cells and germ cells in NOA testes, such as somatic cell immaturity, aberrant growth factor signalling, increased inflammation, increased apoptosis and abnormal extracellular matrix regulation. Future cell-type-specific investigations in identifying modulators of cellular transcription and translation will be key to understanding upstream dysregulation, and these studies will require development of in vitro models to functionally interrogate spermatogenic niche dysfunction in both somatic and germ cells.

Transcriptomic signatures for human male infertility

Introduction: Male infertility is a common, complex disorder. A better understanding of pathogenesis and etiology is needed for timely diagnosis and treatment. The aim of this study, therefore, was to identify genes involved in the pathogenesis of idiopathic male infertility based on data from transcriptomic level supported with data from genomic level. Materials and methods: First, we performed whole gene expression analysis in 20 testis biopsy samples of patients with severely impaired (10) and normal spermatogenesis (10). Further, we have performed systematic review of comparable male infertility studies and overlapped the most significantly expressed genes identified in our study with the most differentially expressed genes from selected studies. Gene Ontology analysis and KEGG functional enrichment have been performed with Enrichr analysis tool. Additionally, we have overlapped these genes with the genes where rare variants have been identified previously. Results: In 10 patients with severely impaired spermatogenesis and 10 controls, we identified more than 1,800 differentially expressed genes (p < 0.001). With the systematic review of three previously performed microarray studies that have met inclusion criteria we identified 257 overlapped differentialy expressed genes (144 downregulated and 113 upregulated). Intersection of genes from transcriptomic studies with genes with identified rare variants revealed a total of 7 genes linked with male infertility phenotype (CYP11A1, CYP17A1, RSPH3, TSGA10, AKAP4, CCIN, NDNF). Conclusion: Our comprehensive study highlighted the role of four genes in pathogenesis of male infertility and provided supporting evidence for three promising candidate genes which dysfunction may result in a male infertility disorder.

DDX58 expression promotes inflammation and growth arrest in Sertoli cells by stabilizing p65 mRNA in patients with Sertoli cell-only syndrome

Sertoli cell -only syndrome (SCOS) is a type of testicular pathological failure that causes male infertility and no effective treatment strategy, is available for this condition. Moreover, the molecular mechanism underlying its development remains unknown. We identified DExD/H-Box helicase 58 (DDX58) as a key gene in SCOS based on four datasets of testicular tissue samples obtained from the Gene Expression Synthesis database. DDX58 was significantly upregulated in SCOS testicular Sertoli cells. Moreover, high expression of DDX58 was positively correlated with the expression of several testicular inflammatory factors, such as IL -1β, IL-18, and IL-6. Interestingly, DDX58 could be induced in the D-galactose (D-gal)-stimulated TM4 cell injury model. Whereas silencing of DDX58 inhibited D-gal -mediated p65 expression, inflammatory cytokine release, and growth arrest. Mechanistically, we found that DDX58 acts as an RNA-binding protein, which enhances p65 expression by promoting mRNA stability. Furthermore, p65 gene silencing decreased the expression of inflammatory cytokines and inhibition of cell growth in D-gal-induced cells. In conclusion, our findings demonstrate that DDX58 promotes inflammatory responses and growth arrest in SCOS Sertoli cells by stabilizing p65 mRNA. Accordingly, the DDX58/p65 regulatory axis might be a therapeutic target for SCOS.

Genome-Wide Association Screening Determines Peripheral Players in Male Fertility Maintenance

Deciphering the functional relationships of genes resulting from genome-wide screens for polymorphisms that are associated with phenotypic variations can be challenging. However, given the common association with certain phenotypes, a functional link should exist. We have tested this prediction in newly sequenced exomes of altogether 100 men representing different states of fertility. Fertile subjects presented with normal semen parameters and had naturally fathered offspring. In contrast, infertile probands were involuntarily childless and had reduced sperm quantity and quality. Genome-wide association study (GWAS) linked twelve non-synonymous single-nucleotide polymorphisms (SNPs) to fertility variation between both cohorts. The SNPs localized to nine genes for which previous evidence is in line with a role in male fertility maintenance: ANAPC1, CES1, FAM131C, HLA-DRB1, KMT2C, NOMO1, SAA1, SRGAP2, and SUSD2. Most of the SNPs residing in these genes imply amino acid exchanges that should only moderately affect protein functionality. In addition, proteins encoded by genes from present GWAS occupied peripheral positions in a protein-protein interaction network, the backbone of which consisted of genes listed in the Online Mendelian Inheritance in Man (OMIM) database for their implication in male infertility. Suggestive of an indirect impact on male fertility, the genes focused were indeed linked to each other, albeit mediated by other interactants. Thus, the chances of identifying a central player in male infertility by GWAS could be limited in general. Furthermore, the SNPs determined and the genes containing these might prove to have potential as biomarkers in the diagnosis of male fertility.

Deviations from Mendelian Inheritance on Bovine X-Chromosome Revealing Recombination, Sex-of-Offspring Effects and Fertility-Related Candidate Genes

Transmission ratio distortion (TRD), or significant deviations from Mendelian inheritance, is a well-studied phenomenon on autosomal chromosomes, but has not yet received attention on sex chromosomes. TRD was analyzed on 3832 heterosomal single nucleotide polymorphisms (SNPs) and 400 pseudoautosomal SNPs spanning the length of the X-chromosome using 436,651 genotyped Holstein cattle. On the pseudoautosomal region, an opposite sire-TRD pattern between male and female offspring was identified for 149 SNPs. This finding revealed unique SNPs linked to a specific-sex (Y- or X-) chromosome and describes the accumulation of recombination events across the pseudoautosomal region. On the heterosomal region, 13 SNPs and 69 haplotype windows were identified with dam-TRD. Functional analyses for TRD regions highlighted relevant biological functions responsible to regulate spermatogenesis, development of Sertoli cells, homeostasis of endometrium tissue and embryonic development. This study uncovered the prevalence of different TRD patterns across both heterosomal and pseudoautosomal regions of the X-chromosome and revealed functional candidate genes for bovine reproduction.

Immune and spermatogenesis-related loci are involved in the development of extreme patterns of male infertility

We conducted a genome-wide association study in a large population of infertile men due to unexplained spermatogenic failure (SPGF). More than seven million genetic variants were analysed in 1,274 SPGF cases and 1,951 unaffected controls from two independent European cohorts. Two genomic regions were associated with the most severe histological pattern of SPGF, defined by Sertoli cell-only (SCO) phenotype, namely the MHC class II gene HLA-DRB1 (rs1136759, P = 1.32E-08, OR = 1.80) and an upstream locus of VRK1 (rs115054029, P = 4.24E-08, OR = 3.14), which encodes a protein kinase involved in the regulation of spermatogenesis. The SCO-associated rs1136759 allele (G) determines a serine in the position 13 of the HLA-DRβ1 molecule located in the antigen-binding pocket. Overall, our data support the notion of unexplained SPGF as a complex trait influenced by common variation in the genome, with the SCO phenotype likely representing an immune-mediated condition.

A GWAS in a large case-control cohort of European ancestry identifies two genomic regions, the MHC class II gene HLA-DRB1 and an upstream locus of VRK1, that are associated with the most severe phenotype of spermatogenic failure.

A Comparative Cross-Platform Analysis to Identify Potential Biomarker Genes for Evaluation of Teratozoospermia and Azoospermia

Male infertility is a global public health concern. Teratozoospermia is a qualitative anomaly of spermatozoa morphology, contributing significantly to male infertility, whereas azoospermia is the complete absence of spermatozoa in the ejaculate. Thus, there is a serious need for unveiling the common origin and/or connection between both of these diseases, if any. This study aims to identify common potential biomarker genes of these two diseases via an in silico approach using a meta-analysis of microarray data. In this study, a differential expression analysis of genes was performed on four publicly available RNA microarray datasets, two each from teratozoospermia (GSE6872 and GSE6967) and azoospermia (GSE145467 and GSE25518). From the analysis, 118 DEGs were found to be common to teratozoospermia and azoospermia, and, interestingly, sperm autoantigenic protein 17 (SPA17) was found to possess the highest fold change value among all the DEGs (9.471), while coiled-coil domain-containing 90B (CCDC90B) and coiled-coil domain-containing 91 (CCDC91) genes were found to be common among three of analyses, i.e., Network Analyst, ExAtlas, and GEO2R. This observation indicates that SPA17, CCDC90B, and CCDC91 genes might have significant roles to play as potential biomarkers for teratozoospermia and azoospermia. Thus, our study opens a new window of research in this area and can provide an important theoretical basis for the diagnosis and treatment of both these diseases.

Genome-wide methylation analyses of human sperm unravel novel differentially methylated regions in asthenozoospermia

Aims & objectives: To investigate DNA methylation patterns in asthenozoospermic and normozoospermic sperm and to explore the potential roles of differential methylations in the etiology of the disease. Materials & methods: The authors performed whole-genome bisulfite sequencing analysis between normozoospermic controls and asthenozoospermic individuals. Results: The authors identified 238 significant differentially methylated regions. These differentially methylated regions were annotated to 114 protein-coding genes, with many genes showing associations with spermatogenesis, sperm motility etc. Conclusion: There are plenty of genomic regions exhibiting altered DNA methylation in asthenozoospermia, a number of which are located within or adjacent to sperm-related genes, suggesting novel methylation markers of asthenozoospermia and potential epigenetic regulation mechanisms through DNA methylation in the disease.

Aberrant Gene Expression Profiling in Men With Sertoli Cell-Only Syndrome

Sertoli cell-only syndrome (SCOS) is the most severe and common pathological type of non-obstructive azoospermia. The etiology of SCOS remains largely unknown to date despite a handful of studies reported in this area. According to the gene expression of testicular tissue samples in six datasets from the Gene Expression Omnibus, we detected 1441 differentially expressed genes (DEGs) between SCOS and obstructive azoospermia (OA) testicular tissue samples. Enriched GO terms and KEGG pathways for the downregulated genes included various terms and pathways related to cell cycle and reproduction, while the enrichment for the upregulated genes yielded many inflammation-related terms and pathways. In accordance with the protein-protein interaction (PPI) network, all genes in the most critical module belonged to the downregulated DEGs, and we obtained nine hub genes, including CCNB1, AURKA, CCNA2, BIRC5, TYMS, UBE2C, CDC20, TOP2A, and OIP5. Among these hub genes, six were also found in the most significant SCOS-specific module obtained from consensus module analysis. In addition, most of SCOS-specific modules did not have a consensus counterpart. Based on the downregulated genes, transcription factors (TFs) and kinases within the upstream regulatory network were predicted. Then, we compared the difference in infiltrating levels of immune cells between OA and SCOS samples and found a significantly higher degree of infiltration for most immune cells in SCOS than OA samples. Moreover, CD56bright natural killer cell was significantly associated with six hub genes. Enriched hallmark pathways in SCOS had remarkably more upregulated pathways than the downregulated ones. Collectively, we detected DEGs, significant modules, hub genes, upstream TFs and kinases, enriched downstream pathways, and infiltrated immune cells that might be specifically implicated in the pathogenesis of SCOS. These findings provide new insights into the pathogenesis of SCOS and fuel future advances in its theranostics.

TCF3 Regulates the Proliferation and Apoptosis of Human Spermatogonial Stem Cells by Targeting PODXL

Spermatogonial stem cells (SSCs) are the initial cells for the spermatogenesis. Although much progress has been made on uncovering a number of modulators for the SSC fate decisions in rodents, the genes mediating human SSCs remain largely unclear. Here we report, for the first time, that TCF3, a member of the basic helix-loop-helix family of transcriptional modulator proteins, can stimulate proliferation and suppress the apoptosis of human SSCs through targeting podocalyxin-like protein (PODXL). TCF3 was expressed primarily in GFRA1-positive spermatogonia, and EGF (epidermal growth factor) elevated TCF3 expression level. Notably, TCF3 enhanced the growth and DNA synthesis of human SSCs, whereas it repressed the apoptosis of human SSCs. RNA sequencing and chromatin immunoprecipitation (ChIP) assays revealed that TCF3 protein regulated the transcription of several genes, including WNT2B, TGFB3, CCN4, MEGF6, and PODXL, while PODXL silencing compromised the stem cell activity of SSCs. Moreover, the level of TCF3 protein was remarkably lower in patients with spermatogenesis failure when compared to individuals with obstructive azoospermia with normal spermatogenesis. Collectively, these results implicate that TCF3 modulates human SSC proliferation and apoptosis through PODXL. This study is of great significance since it would provide a novel molecular mechanism underlying the fate determinations of human SSCs and it could offer new targets for gene therapy of male infertility.

Mitochondria Content and Activity Are Crucial Parameters for Bull Sperm Quality Evaluation

Standard sperm evaluation parameters do not enable predicting their ability to survive cryopreservation. Mitochondria are highly prone to suffer injuries during freezing, and any abnormalities in their morphology or function are reflected by a decline of sperm quality. Our work focused on describing a link between the number and the activity of mitochondria, with an aim to validate its applicability as a biomarker of bovine sperm quality. Cryopreserved sperm collected from bulls with high (group 1) and low (group 2) semen quality was separated by swim up. The spermatozoa of group 1 overall retained more mitochondria (MitoTrackerGreen) and mtDNA copies, irrespective of the fraction. Regardless of the initial ejaculate quality, the motile sperm contained significantly more mitochondria and mtDNA copies. The same trend was observed for mitochondrial membrane potential (ΔΨm, JC-1), where motile sperm displayed high ΔΨm. These results stay in agreement with transcript-level evaluation (real-time polymerase chain reaction, PCR) of antioxidant enzymes (PRDX1, SOD1, GSS), which protect cells from the reactive oxygen species. An overall higher level of glutathione synthetase (GSS) mRNA was noted in group 1 bulls, suggesting higher ability to counteract free radicals. No differences were noted between basal oxygen consumption rate (OCR) (Seahorse XF Agilent) and ATP-linked respiration for group 1 and 2 bulls. In conclusion, mitochondrial content and activity may be used as reliable markers for bovine sperm quality evaluation.

Hypertension and reproductive dysfunction: a possible role of inflammation and inflammation-associated lymphangiogenesis in gonads

Hypertension is one of the most prevalent diseases that leads to end organ damage especially affecting the heart, kidney, brain, and eyes. Numerous studies have evaluated the association between hypertension and impaired sexual health, in both men and women. The detrimental effects of hypertension in men includes erectile dysfunction, decrease in semen volume, sperm count and motility, and abnormal sperm morphology. Similarly, hypertensive females exhibit decreased vaginal lubrication, reduced orgasm, and several complications in pregnancy leading to fetal and maternal morbidity and mortality. The adverse effect of hypertension on male and female fertility is attributed to hormonal imbalance and changes in the gonadal vasculature. However, mechanistic studies investigating the impact of hypertension on gonads in more detail on a molecular basis remain scarce. Hence, the aim of the current review is to address and summarize the effects of hypertension on reproductive health, and highlight the importance of research on the effects of hypertension on gonadal inflammation and lymphatics.

Long noncoding RNAs expression profile and long noncoding RNA-mediated competing endogenous RNA network in nonobstructive azoospermia patients

Aim: To analyze the expression profile and competing endogenous RNA (ceRNA) network of long noncoding RNAs (lncRNAs) in nonobstructive azoospermia (NOA). Materials & methods: The lncRNA expression profile in NOA was determined by microarray reanalysis. Differential expression analysis was performed by R software. The ceRNA network was constructed using correlation analysis and gene target miRNA prediction. Metascape was used for enrichment analysis. Again ceRNA network was validated by quantitative real-time PCR. Results: Many lncRNAs are differently expressed in NOA. LncRNAs might participate in spermatogenesis through ceRNA mechanism. The ceRNA network included male gamete generation and other pathways. LINC00467 in the network regulated the expression of LRGUK and TDRD6. Conclusion: LncRNAs are involved in NOA and potential biomarkers and therapeutic targets for NOA.

Upregulation of the RNF8 gene can predict the presence of sperm in azoospermic individuals

Objective

In this study, specimens from testicular biopsies of men with nonobstructive azoospermia (NOA) were used to investigate whether RNF8 gene could serve as a biomarker to predict the presence of sperm in these patients.

Methods

Testicular biopsy specimens from 47 patients were classified according to the presence of sperm (positive vs. negative groups) and investigated for the expression of RNF8. The level of RNF8 gene expression in the testes was compared between these groups using reverse-transcription polymerase chain reaction.

Results

The expression level of RNF8 was significantly higher in testicular samples from the positive group than in those from the negative group. Moreover, the area under the curve of RNF8 expression for the entire study population was 0.84, showing the discriminatory power of RNF8 expression in differentiating between the positive and negative groups of men with NOA. A receiver operating characteristic curve analysis showed that RNF8 expression had a sensitivity of 81% and a specificity of 84%, with a cutoff level of 1.76.

Conclusion

This study points out a significant association between the expression of RNF8 and the presence of sperm in NOA patients, which suggests that quantified RNF8 expression in testicular biopsy samples may be a valuable biomarker for predicting the presence of spermatozoa in biopsy samples.

The potential impact of tumor suppressor genes on human gametogenesis: a case-control study

PURPOSE

To study the incidence of tumor suppressor gene (TSG) mutations in men and women with impaired gametogenesis.

METHODS

Gene association analyses were performed on blood samples in two distinct patient populations: males with idiopathic male infertility and females with unexplained diminished ovarian reserve (DOR). The male study group consisted of men with idiopathic azoospermia, oligozoospermia, asthenozoospermia, or teratozoospermia. Age-matched controls were men with normal semen analyses. The female study group consisted of women with unexplained DOR with anti-Müllerian hormone levels ≤ 1.1 ng/mL. Controls were age-matched women with normal ovarian reserve (> 1.1 ng/mL).

RESULTS

Fifty-seven male cases (mean age = 38.4; mean sperm count = 15.7 ± 12.1; mean motility = 38.2 ± 24.7) and 37 age-matched controls (mean age = 38.0; mean sperm count = 89.6 ± 37.5; mean motility = 56.2 ± 14.3) were compared. Variants observed in CHD5 were found to be enriched in the study group (p = 0.000107). The incidence of CHD5 mutation c.*3198_*3199insT in the 3'UTR (rs538186680) was significantly higher in cases compared to controls (p = 0.0255). 72 DOR cases (mean age = 38.7; mean AMH = 0.5 ± 0.3; mean FSH = 11.7 ± 12.5) and 48 age-matched controls (mean age = 37.6; mean AMH = 4.1 ± 3.0; mean FSH = 7.1 ± 2.2) were compared. Mutations in CHD5 (c.-140A>C), RB1 (c.1422-18delT, rs70651121), and TP53 (c.376-161A>G, rs75821853) were found at significantly higher frequencies in DOR cases compared to controls (p ≤ 0.05). In addition, 363 variants detected in the DOR patients were not present in the control group.

CONCLUSION

Unexplained impaired gametogenesis in both males and females may be associated with genetic variation in TSGs. TSGs, which play cardinal roles in cell-cycle control, might also be critical for normal spermatogenesis and oogenesis. If validated in larger prospective studies, it is possible that TSGs provide an etiological basis for some patients with impaired gametogenesis.

Multiple signaling pathways in Sertoli cells: recent findings in spermatogenesis

The functions of Sertoli cells in spermatogenesis have attracted much more attention recently. Normal spermatogenesis depends on Sertoli cells, mainly due to their influence on nutrient supply, maintenance of cell junctions, and support for germ cells' mitosis and meiosis. Accumulating evidence in the past decade has highlighted the dominant functions of the MAPK, AMPK, and TGF-β/Smad signaling pathways during spermatogenesis. Among these pathways, the MAPK signaling pathway regulates dynamics of tight junctions and adherens junctions, proliferation and meiosis of germ cells, proliferation and lactate production of Sertoli cells; the AMPK and the TGF-β/Smad signaling pathways both affect dynamics of tight junctions and adherens junctions, as well as the proliferation of Sertoli cells. The AMPK signaling pathway also regulates lactate supply. These signaling pathways combine to form a complex regulatory network for spermatogenesis. In testicular tumors or infertile patients, the activities of these signaling pathways in Sertoli cells are abnormal. Clarifying the mechanisms of signaling pathways in Sertoli cells on spermatogenesis provides new insights into the physiological functions of Sertoli cells in male reproduction, and also serves as a pre-requisite to identify potential therapeutic targets in abnormal spermatogenesis including testicular tumor and male infertility.

Genetic mechanisms underlying spermatic and testicular traits within and among cattle breeds: systematic review and prioritization of GWAS results

Reduced bull fertility imposes economic losses in bovine herds. Specifically, testicular and spermatic traits are important indicators of reproductive efficiency. Several genome-wide association studies (GWAS) have identified genomic regions associated with these fertility traits. The aims of this study were as follows: 1) to perform a systematic review of GWAS results for spermatic and testicular traits in cattle and 2) to identify key functional candidate genes for these traits. The identification of functional candidate genes was performed using a systems biology approach, where genes shared between traits and studies were evaluated by a guilt by association gene prioritization (GUILDify and ToppGene software) in order to identify the best functional candidates. These candidate genes were integrated and analyzed in order to identify overlapping patterns among traits and breeds. Results showed that GWAS for testicular-related traits have been developed for beef breeds only, whereas the majority of GWAS for spermatic-related traits were conducted using dairy breeds. When comparing traits measured within the same study, the highest number of genes shared between different traits was observed, indicating a high impact of the population genetic structure and environmental effects. Several chromosomal regions were enriched for functional candidate genes associated with fertility traits. Moreover, multiple functional candidate genes were enriched for markers in a species-specific basis, taurine (Bos taurus) or indicine (Bos indicus). For the different candidate regions identified in the GWAS in the literature, functional candidate genes were detected as follows: B. Taurus chromosome X (BTX) (TEX11, IRAK, CDK16, ATP7A, ATRX, HDAC6, FMR1, L1CAM, MECP2, etc.), BTA17 (TRPV4 and DYNLL1), and BTA14 (MOS, FABP5, ZFPM2). These genes are responsible for regulating important metabolic pathways or biological processes associated with fertility, such as progression of spermatogenesis, control of ciliary activity, development of Sertoli cells, DNA integrity in spermatozoa, and homeostasis of testicular cells. This study represents the first systematic review on male fertility traits in cattle using a system biology approach to identify key candidate genes for these traits.

Fine mapping the MHC region identified rs4997052 as a new variant associated with nonobstructive azoospermia in Han Chinese males

OBJECTIVE

To investigate the association between genetic variants in the major histocompatibility complex (MHC) region and nonobstructive azoospermia (NOA) susceptibility.

DESIGN

MHC region fine-mapping analysis based on previous NOA genome-wide association study (GWAS) data.

SETTING

Medical university.

PATIENT(S)

Nine hundred and eighty-one men with NOA and 1,657 normal fertile male controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The MHC region imputation assessed with SNP2HLA software, taking the specific Han-MHC database as a reference panel; statistical significance of the MHC variants calculated using logistic regression models; functional annotation based on online public databases; and phenotypic variances explained by specific groups of genetic variants estimated using the fixed effects model from individual associations.

RESULT(S)

Two independent risk loci, rs7194 (odds ratio [OR] 1.37) at MHC class II molecules and rs4997052 (OR 1.30) at MHC class I molecules, were identified. Functional annotation showed rs7194 may tag the effect of multiple amino acid residues and the expression of HLA-DQB1 and HLA-DRB1; while rs4997052 showed the effect of amino acid changes of HLA-B at position 116 as well as the expression of HLA-B and CCHCR1, which coexpressed with genes enriched in pathways of spermatogenesis and male gamete generation. The novel variant rs4997052 identified in our study can explain another approximately 0.66% of the phenotypic variances of NOA.

CONCLUSION(S)

We fine-mapped the MHC region and identified two loci that independently drove NOA susceptibility. These results provide a deeper understanding of the association mechanisms of MHC and NOA risk.

New transcriptomic tools to understand testis development and functions

The testis plays a central role in the male reproductive system - secreting several hormones including male steroids and producing male gametes. A complex and coordinated molecular program is required for the proper differentiation of testicular cell types and maintenance of their functions in adulthood. The testicular transcriptome displays the highest levels of complexity and specificity across all tissues in a wide range of species. Many studies have used high-throughput sequencing technologies to define the molecular dynamics and regulatory networks in the testis as well as to identify novel genes or gene isoforms expressed in this organ. This review intends to highlight the complementarity of these transcriptomic studies and to show how the use of different sequencing protocols contribute to improve our global understanding of testicular biology.

Transcriptome-wide association study revealed two novel genes associated with nonobstructive azoospermia in a Chinese population

OBJECTIVE

To investigate the associations between genetically cis-regulated gene expression levels and nonobstructive azoospermia (NOA) susceptibility.

DESIGN

Transcriptome-wide association study (TWAS).

SETTING

Medical university.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE(S)

The cis-hg² values for each gene were estimated with GCTA software. The effect sizes of cis-single-nucleotide polymorphisms (SNPs) on gene expression were measured using GEMMA software. Gene expression levels were entered into our existing NOA GWAS cohort using GEMMA software. The TWAS P-values were calculated using logistic regression models.

RESULT(S)

Expression levels of 1,296 cis-heritable genes were entered into our existing NOA GWAS data. The TWAS results identified two novel genes as statistically significantly associated with NOA susceptibility: PILRA and ZNF676. In addition, 6p21.32, previously reported in NOA GWAS, was further validated to be a susceptible region to NOA risk.

CONCLUSION(S)

Analysis with TWAS provides fruitful targets for follow-up functional studies.

SLY regulates genes involved in chromatin remodeling and interacts with TBL1XR1 during sperm differentiation

Sperm differentiation requires unique transcriptional regulation and chromatin remodeling after meiosis to ensure proper compaction and protection of the paternal genome. Abnormal sperm chromatin remodeling can induce sperm DNA damage, embryo lethality and male infertility, yet, little is known about the factors which regulate this process. Deficiency in Sly, a mouse Y chromosome-encoded gene expressed only in postmeiotic male germ cells, has been shown to result in the deregulation of hundreds of sex chromosome-encoded genes associated with multiple sperm differentiation defects and subsequent male infertility. The underlying mechanism remained, to date, unknown. Here, we show that SLY binds to the promoter of sex chromosome-encoded and autosomal genes highly expressed postmeiotically and involved in chromatin regulation. Specifically, we demonstrate that Sly knockdown directly induces the deregulation of sex chromosome-encoded H2A variants and of the H3K79 methyltransferase DOT1L. The modifications prompted by loss of Sly alter the postmeiotic chromatin structure and ultimately result in abnormal sperm chromatin remodeling with negative consequences on the sperm genome integrity. Altogether our results show that SLY is a regulator of sperm chromatin remodeling. Finally we identified that SMRT/N-CoR repressor complex is involved in gene regulation during sperm differentiation since members of this complex, in particular TBL1XR1, interact with SLY in postmeiotic male germ cells.

Cytokines in Male Fertility and Reproductive Pathologies: Immunoregulation and Beyond

Germline development in vivo is dependent on the environment formed by somatic cells and the differentiation cues they provide; hence, the impact of local factors is highly relevant to the production of sperm. Knowledge of how somatic and germline cells interact is central to achieving biomedical goals relating to restoring, preserving or restricting fertility in humans. This review discusses the growing understanding of how cytokines contribute to testicular function and maintenance of male reproductive health, and to the pathologies associated with their abnormal activity in this organ. Here we consider both cytokines that signal through JAKs and are regulated by SOCS, and those utilizing other pathways, such as the MAP kinases and SMADs. The importance of cytokines in the establishment and maintenance of the testis as an immune-privilege site are described. Current research relating to the involvement of immune cells in testis development and disease is highlighted. This includes new data relating to testicular cancer which reinforce the understanding that tumorigenic cells shape their microenvironment through cytokine actions. Clinical implications in pathologies relating to local inflammation and to immunotherapies are discussed.

Lipopolysaccharide Compromises Human Sperm Function by Reducing Intracellular cAMP

A worldwide decline in the quality of human semen is currently occurring. In mammals, sperm are produced from diploid stem-cell spermatogonia by spermatogenesis in testes and become mature in epididymis. Nevertheless, these biological processes can be affected by Gram-negative bacterial infection mediated by lipopolysaccharide (LPS), the major endotoxin of Gram-negative bacteria. It is well known that LPS can disturb spermatogenesis and affect sperm maturation and quality in vivo. However, the effect of LPS on the ejaculated mature sperm in vitro remains unclear. Thus, this study aimed to assess the in vitro toxicity of LPS on human sperm function and to elucidate the underlying mechanism. Human sperm were incubated with LPS (0.1-100 μg/ml) for 1-12 h in vitro and, subsequently, sperm viability, motility and capacitation, and the acrosome reaction were examined. LPS dose-dependently inhibited total and progressive motility and the ability to move through a viscous medium of the sperm but did not affect sperm viability, capacitation, and the acrosome reaction. To explore the underlying mechanism of LPS's actions, we examined the effects of LPS on the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca(2+)]i) and protein-tyrosine phosphorylation of human sperm, which are key regulators of human sperm function. LPS decreased intracellular cAMP dose-dependently but had no effect on [Ca(2+)]i and protein-tyrosine phosphorylation of human sperm. These findings suggest that LPS inhibits human sperm motility by decreasing intracellular cAMP.

GnT1IP-L specifically inhibits MGAT1 in the Golgi via its luminal domain

Mouse GnT1IP-L, and membrane-bound GnT1IP-S (MGAT4D) expressed in cultured cells inhibit MGAT1, the N-acetylglucosaminyltransferase that initiates the synthesis of hybrid and complex N-glycans. However, it is not known where in the secretory pathway GnT1IP-L inhibits MGAT1, nor whether GnT1IP-L inhibits other N-glycan branching N-acetylglucosaminyltransferases of the medial Golgi. We show here that the luminal domain of GnT1IP-L contains its inhibitory activity. Retention of GnT1IP-L in the endoplasmic reticulum (ER) via the N-terminal region of human invariant chain p33, with or without C-terminal KDEL, markedly reduced inhibitory activity. Dynamic fluorescent resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) assays revealed homomeric interactions for GnT1IP-L in the ER, and heteromeric interactions with MGAT1 in the Golgi. GnT1IP-L did not generate a FRET signal with MGAT2, MGAT3, MGAT4B or MGAT5 medial Golgi GlcNAc-tranferases. GnT1IP/Mgat4d transcripts are expressed predominantly in spermatocytes and spermatids in mouse, and are reduced in men with impaired spermatogenesis.

DOI:http://dx.doi.org/10.7554/eLife.08916.001

Proteins are made up of chains of amino acids that fold into three-dimensional shapes and many are assembled in a cell compartment known as the endoplasmic reticulum. From here, these new proteins move to another compartment called the Golgi, where they may be further modified before they are transported to their final destination in the cell.

One way that proteins may be modified is known as glycosylation, in which sugar molecules are attached to specific amino acids. Some sugar molecules can act as labels that ensure the new proteins are transported to the correct destination in the cell. For proteins that are delivered to the surface of the cell, the sugar molecules can also play important roles in communication with other cells.

A simple sugar molecule, or a complex arrangement of many sugar molecules, may be attached to an amino acid by glycosylation. An enzyme called MGAT1 controls the synthesis of sugars called complex N-glycans in the Golgi. In 2010, researchers reported that a glycoprotein called GnT1IP-L binds to MGAT1 and inhibits its activity, thereby blocking the production of complex N-glycans. GnT1IP-L was found in the endoplasmic reticulum and Golgi, but it was not clear how it inhibits MGAT1.

Huang et al.—including some of the researchers from the 2010 study—have now investigated the activity of GnT1IP-L in cells grown in the laboratory using several biochemical techniques. The experiments show that GnT1IP-L only binds to MGAT1 when both proteins are in the Golgi. There are three sections (or ‘domains’) in GnT1IP-L, but Huang et al. found that only the domain that is on the inside of the Golgi is involved in this interaction.

Previous work indicated that GnT1IP-L may be involved in the formation of sperm in mice. Huang et al. have now analyzed previously published data on samples of testis tissue from human patients and found that the gene that encodes GnT1IP-L is present in very low amounts in patients whose sperm do not develop properly.

Huang et al.'s findings suggest that GnT1IP-L may inhibit MGAT1 to control the glycosylation of proteins in the Golgi of developing sperm. The next step is to test this hypothesis by generating mutant mice that lack GnT1IP-L, or to make GnT1P-L in other cells in which it is not normally made, to find out if this affects the production of sperm.

DOI:http://dx.doi.org/10.7554/eLife.08916.002

Angiotensin II regulates testicular peritubular cell function via AT1 receptor: a specific situation in male infertility

We observed that peritubular myoid cells in the human testis are immunoreactive for angiotensin II (AngII) receptors (AT1R) and explored AngII actions in cultured human testicular peritubular cells (HTPCs). In response to AngII they contracted within minutes. The AT1R-blocker losartan blocked contraction, implying involvement of AngII and AT1R in intratesticular sperm transport. AngII also significantly increased IL-6 mRNA levels and IL-6 secretion within hours and losartan again prevented this action. This suggests involvement in inflammatory processes, which may play a role in male infertility. AngII can be generated locally by mast cell (MC)-derived chymase (CHY), which cleaves AngI. In testicular biopsies from infertile men we found abundant MCs, which express CHY, within the wall of seminiferous tubules. In contrast, CHY-positive MCs are hardly found in normal human testis. Testicular inflammatory events may fuel processes resulting in impaired spermatogenesis. Therefore therapeutic interference with MCs, CHY or AT1R might be novel options in male infertility.

Chd5 orchestrates chromatin remodelling during sperm development

One of the most remarkable chromatin remodelling processes occurs during spermiogenesis, the post-meiotic phase of sperm development during which histones are replaced with sperm-specific protamines to repackage the genome into the highly compact chromatin structure of mature sperm. Here we identify Chromodomain helicase DNA binding protein 5 (Chd5) as a master regulator of the histone-to-protamine chromatin remodelling process. Chd5 deficiency leads to defective sperm chromatin compaction and male infertility in mice, mirroring the observation of low CHD5 expression in testes of infertile men. Chd5 orchestrates a cascade of molecular events required for histone removal and replacement, including histone 4 (H4) hyperacetylation, histone variant expression, nucleosome eviction and DNA damage repair. Chd5 deficiency also perturbs expression of transition proteins (Tnp1/Tnp2) and protamines (Prm1/2). These findings define Chd5 as a multi-faceted mediator of histone-to-protamine replacement and depict the cascade of molecular events underlying this process of extensive chromatin remodelling.

PLIN1 deficiency affects testicular gene expression at the meiotic stage in the first wave of spermatogenesis

PLIN1, a lipid droplet associated protein, has been implicated in playing a key role in the regulation of lipolysis and lipid storage in adipocytes. PLIN1 is found to be highly expressed in Leydig cells of testis, suggesting a potential role in steroidogenesis and spermatogenesis. In this study, we showed that PLIN1 was expressed in testis and that its mRNA levels declined significantly with development. To investigate the role of PLIN1, we take advantage of PLIN1-null mice. We found that the number of seminiferous tubules containing round spermatids was significantly increased at P21 (postnatal day 21). Furthermore, microarray analysis showed that there were 538 differentially expressed genes between PLIN1-null and wild-type mice at P21. The up-regulated genes in knockout mice were enriched in spermatogenesis by Gene Ontology classification. Among them, Prm1 and Wbp2nl are important for spermatogenesis which were confirmed by real-time PCR. Unexpectedly, the levels of serum testosterone and serum 17β-estradiol as well as steroidogenic genes are not altered in the PLIN1-null mice. Compared to the wild-type mice, no significant difference of fertility was found in the PLIN1-null mice. Therefore, these findings indicated that PLIN1 disruption leads to the increase of round spermatid-containing seminiferous tubules at the meiotic stage of the first wave of spermatogenesis through regulating spermatogenic related genes.

Cytogenetic and molecular analyses of de novo translocation dic(9;13)(p11.2;p12) in an infertile male

BACKGROUND

Whole arm t(9;13)(p11;p12) translocations are rare and have been described only a few times; all of the previously reported cases were familial.

RESULTS

We present here an infertile male carrier with a whole-arm reciprocal translocation dic(9;13)(p11.2;p12) revealed by GTG-, C-, and NOR-banding karyotypes with no mature sperm cells in his ejaculate. FISH and genome-wide 400 K CGH microarray (Agilent) analyses demonstrated a balanced chromosome complement and further characterised the abnormality as a dicentric chromosome (9;13): dic(9;13)(pter→p11.2::p12→qter),neo(9)(pter→p12→neo→p11.2). An analysis of the patient's ejaculated cells identified immature germ cells at different phases of spermatogenesis but no mature spermatozoa. Most (82.5%) of the germ cells were recognised as spermatocytes at stage I, and the cell nuclei were most frequently found in pachytene I (41.8%). We have also undertaken FISH analysis and documented an increased rate of aneuploidy of chromosomes 15, 18, X and Y in the peripheral blood leukocytes of our patient. To study the aneuploidy risk in leukocytes, we have additionally included 9 patients with non-obstructive azoospermia with normal karyotypes.

CONCLUSIONS

We propose that the azoospermia observed in the patient with the dic(9;13)(p11.2;p12) translocation was most likely a consequence of a very high proportion (90%) of association between XY bivalents and quadrivalent formations in prophase I.

Semen analysis: update on clinical value, current needs and future perspectives

At present, evaluation of male reproductive function consists primarily of routine semen analysis, a collection of conventional microscopic assessments ideally performed following the guidelines set by the World Health Organization. While providing some insight into testicular function, these long-performed tests are limited in the information that they impart; more specifically, they are unable to predict true fertility potential. As a consequence, there is a need for the appraisal and consideration of newer semen parameters that may be more indicative of reproductive success. Although various novel assays have been introduced that broaden the scope of information available to both researcher and clinician, the utility of these tests remains limited due to the lack of standardisation of protocols and the absence of clinically established, dependable reference ranges. As such, it is not surprising that most of these parameters and their associated methods remain recommended for ‘research purposes only’. With the burgeoning ‘omics’ revolution, nanotechnology and the development of new analytical instruments, there is now an opportunity for the identification and measurement of previously unknown features that may prove to be more indicative of each sperm's true functional status and capability. Once optimised, simplified, clinically validated and made more readily accessible, these new approaches hold the promise of forming the fulcrum upon which andrological investigations can enter a new era.

Potential biomarkers of nonobstructive azoospermia identified in microarray gene expression analysis

OBJECTIVE

To identify potential biomarkers of azoospermia to determine a particular stage of spermatogenetic differentiation.

DESIGN

GeneChip Human Gene 1.0 ST microarray with validation at mRNA and protein levels.

SETTING

Basic research laboratory.

PATIENT(S)

Men with various types of nonobstructive azoospermia (n = 18) and with normal spermatogenesis (n = 4).

INTERVENTION(S)

Obtaining 31 testicular biopsy samples.

MAIN OUTCOME MEASURE(S)

Gene expression analysis using the Affymetrix Human Gene 1.0 ST microarrays on 14 selected genes according to the highest fold change, verified with quantitative polymerase chain reaction and on independent set of microarray samples. Western blot and immunohistochemistry were additionally performed.

RESULT(S)

The comparative analysis of gene expression profiles in the infertile and control groups resulted in the selection of 4,946 differentially expressed genes. AKAP4, UBQLN3, CAPN11, GGN, SPACA4, SPATA3, and FAM71F1 were the most significantly down-regulated genes in infertile patients. Global analysis also led to identification of up-regulated genes-WBSCR28, ADCY10, TMEM225, SPATS1, FSCN3, GTSF1L, and GSG1-in men with late maturation arrest. Moreover, the results from quantitative polymerase chain reaction and Western blot largely confirmed the microarray data.

CONCLUSION(S)

The set of selected genes can be used to create a molecular diagnostic tool to determine the degree of spermatogenic impairment for men with idiopathic nonobstructive azoospermia.

A combined approach facilitates the reliable detection of human spermatogonia in vitro

STUDY QUESTION

Does a combined approach allow for the unequivocal detection of human germ cells and particularly of spermatogonia in vitro?

SUMMARY ANSWER

Based on our findings, we conclude that an approach comprising: (i) the detailed characterization of patients and tissue samples prior to the selection of biopsies, (ii) the use of unambiguous markers for the characterization of cultures and (iii) the use of biopsies lacking the germ cell population as a negative control is the prerequisite for the establishment of human germ cell cultures.

WHAT IS KNOWN ALREADY

The use of non-specific marker genes and the failure to assess the presence of testicular somatic cell types in germ cell cultures may have led to a misinterpretation of results and the erroneous description of germ cells in previous studies.

STUDY DESIGN, SIZE, DURATION

Testicular biopsies were selected from a pool of 264 consecutively obtained biopsies. Based on the histological diagnosis, biopsies with distinct histological phenotypes were selected (n = 35) to analyze the expression of germ cell and somatic cell markers. For germ cell culture experiments, gonadotrophin levels and clinical data were used as selection criteria resulting in the following two groups: (i) biopsies with qualitatively intact spermatogenesis (n = 4) and (ii) biopsies from Klinefelter syndrome Klinefelter patients lacking the germ cell population (n = 3).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Quantitative real-time PCR analyses were performed to evaluate the specificity of 18 selected germ cell and 3 somatic marker genes. Cell specificity of individual markers was subsequently validated using immunohistochemistry. Finally, testicular cell cultures were established and were analyzed after 10 days for the expression of germ cell- (UTF1, FGFR3, MAGE A4, DDX4) and somatic cell-specific markers (SMA, VIM, LHCGR) at the RNA and the protein levels.

MAIN RESULTS AND THE ROLE OF CHANCE

Interestingly, only 9 out of 18 marker genes reflected the presence of germ cells and cell specificity could be validated using immunohistochemistry. Furthermore, VIM, SMA and LHCGR were found to reflect the presence of testicular somatic cells at the RNA and the protein levels. Using this validated marker panel and biopsies lacking the germ cell population (n = 3) as a negative control, we demonstrated that germ cell cultures containing spermatogonia can be established from biopsies with normal spermatogenesis (n = 4) and that these cultures can be maintained for the period of 10 days. However, marker profiling has to be performed at regular time points as the composition of testicular cell types may continuously change under longer term culture conditions.

LIMITATIONS, REASONS FOR CAUTION

There are significant differences regarding the spermatogonial stem cell (SSC) system and spermatogenesis between rodents and primates. It is therefore possible that marker genes that do not reflect the presence of spermatogonia in the human are specific for spermatogonia in other animal models.

WIDER IMPLICATIONS OF THE FINDINGS

While some studies have reported that human SSCs can be maintained in vitro and show characteristics of pluripotency, the germ cell origin and the differentiation potential of these cells were subsequently called into question. This study provides critical insights into possible sources for the misinterpretation of results regarding the presence of germ cells in human testicular cell cultures and our findings can therefore help to avoid conflicting reports in the future.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported by the Stem Cell Network North Rhine-Westphalia and the Innovative Medical Research of the University of Münster Medical School (Grant KO111014). In addition, it was funded by the DFG-Research Unit FOR 1041 Germ Cell Potential (GR 1547/11-1 and SCHL 394/11-2), the BMBF (01GN0809/10) and the IZKF (CRA 03/09). The authors declare that there is no conflict of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Broad DNA methylation changes of spermatogenesis, inflammation and immune response-related genes in a subgroup of sperm samples for assisted reproduction

Aberrant sperm DNA methylation patterns, mainly in imprinted genes, have been associated with male subfertility and oligospermia. Here, we performed a genome-wide methylation analysis in sperm samples representing a wide range of semen parameters. Sperm DNA samples of 38 males attending a fertility centre were analysed with Illumina HumanMethylation27 BeadChips, which quantify methylation of >27 000 CpG sites in cis-regulatory regions of almost 15 000 genes. In an unsupervised analysis of methylation of all analysed sites, the patient samples clustered into a major and a minor group. The major group clustered with samples from normozoospermic healthy volunteers and, thus, may more closely resemble the normal situation. When correlating the clusters with semen and clinical parameters, the sperm counts were significantly different between groups with the minor group exhibiting sperm counts in the low normal range. A linear model identified almost 3000 CpGs with significant methylation differences between groups. Functional analysis revealed a broad gain of methylation in spermatogenesis-related genes and a loss of methylation in inflammation- and immune response-related genes. Quantitative bisulfite pyrosequencing validated differential methylation in three of five significant candidate genes on the array. Collectively, we identified a subgroup of sperm samples for assisted reproduction with sperm counts in the low normal range and broad methylation changes (affecting approximately 10% of analysed CpG sites) in specific pathways, most importantly spermatogenesis-related genes. We propose that epigenetic analysis can supplement traditional semen parameters and has the potential to provide new insights into the aetiology of male subfertility.

The gene expression analysis of paracrine/autocrine factors in patients with spermatogenetic failure compared with normal spermatogenesis

PROBLEM

The aim of this study was to examine the expression levels of IL-1 family members, IL-6, IL-10, TNF family, SCF, and c-kit in infertile patients with idiopathic non-obstructive azoospermia (NOA) compared with men with normal spermatogenesis.

METHOD OF STUDY

We analyzed 20 testicular biopsy samples with Affymetrix Human Gene 1.0 ST microarrays (Affymetrix, Santa Clara, CA, USA). Sixteen of them were obtained from patients with various types of NOA and four with normal spermatogenesis.

RESULTS

The comparative analysis of normal and pathological group demonstrated a different expression level of IL1-RA gene. It was also observed that the gene expression levels for IL1-R1, CASP1, and stem cell factor (SCF) were upregulated in the Sertoli-cell-only syndrome group in comparison with the control one (P < 0.05).

CONCLUSION

The microarray analysis showed the expression level of all investigated paracrine/autocrine factors at one go, and therefore, the possible interaction between these genes could be examined.

Human testicular peritubular cells: more than meets the eye

In healthy men, several layers of inconspicuously flat cells and extracellular matrix (ECM) proteins build the wall of the seminiferous tubules. The cells of this wall, peritubular cells, are not well characterized. They are smooth-muscle-like and contractile and transport immotile sperm, a function important for male fertility. However, their full functional importance, especially their potential contribution to the paracrine regulation of the male gonad, is unknown. In men with impaired spermatogenesis, the architecture of the tubular wall is frequently altered. Deposits of ECM and morphological changes of peritubular cells imply that functions of peritubular cells may be fundamentally altered. To be able to study human peritubular cells and their functions, a culture method was established. It is based on small biopsies of patients with obstructive azoospermia but normal spermatogenesis (human testicular peritubular cells, HTPCs) and non-obstructive azoospermia, impaired spermatogenesis, and testicular fibrosis (HTPCFs). Results obtained from cellular studies and parallel examinations of biopsies provide insights into the repertoire of the secretion products, contractile properties, and plasticity of human peritubular cells. They produce ECM components, including the proteoglycan decorin, which may influence paracrine signaling between testicular cells. They may contribute to the spermatogonial stem cell niche via secreted factors. They are regulated by mast cell and macrophage products, and in response produce factors that can fuel inflammatory changes. They possess a high degree of plasticity, which results in hypertrophy and loss of contractile abilities. The data collectively indicate important roles of inconspicuous testicular peritubular cells in human male fertility and infertility.

Partial loss of contractile marker proteins in human testicular peritubular cells in infertility patients

Fibrotic remodelling of the testicular tubular wall is common in human male infertility caused by impaired spermatogenesis. We hypothesized that this morphological change bears witness of an underlying fundamentally altered state of the cells building this wall, that is, peritubular smooth muscle-like cells. This could include a loss of the contractile abilities of these cells and thus be a factor in male infertility. Immune cells are increased in the tubular wall in these cases, hence local immune cell-related factors, including a prostaglandin (PG) metabolite may be involved. To explore these points in the human, we used testicular biopsies, in which tubules with normal spermatogenesis and impaired spermatogenesis are next to each other [mixed atrophy (MA)], normal biopsies and cultured human testicular peritubular cells. Proteins essential for contraction, myosin heavy chain (MYH11), calponin (Cal) and relaxation, cGMP-dependent protein kinase 1 (cGKI), were readily detected by immunohistochemistry and were equally distributed in all peritubular cells of biopsies with normal spermatogenesis. In all biopsies, vascular smooth muscle cells also stained and served as important intrinsic controls, which showed that in MA samples when spermatogenesis was impaired, staining was restricted to only few peritubular cells or was absent. When spermatogenesis was normal, regular peritubular staining became obvious. This pattern suggests complex regulatory influences, which in face of the identical systemic hormonal situation in MA patients, are likely caused by the local testicular micromilieu. The PG metabolite 15dPGJ2 may represent such a factor and it reduced Cal protein levels in peritubular cells from patients with/without impaired spermatogenesis. The documented phenotypic switch of peritubular, smooth muscle-like cells in MA patients may impair the abilities of the afflicted seminiferous tubules to contract and relax and must now be considered as a part of the complex events in male infertility.

Key functional genes of spermatogenesis identified by microarray analysis

At present many couples face difficulties when trying to conceive that may have a genetic basis. The male factor is the cause of infertility as often as the female. Therefore it is important to identify key genes involved in spermatogenesis which may be linked to male infertility. This review discusses the identification of a range of genes associated with male fertility using microarrays. Based on differences in gene expression profiles between fertile and infertile male subgroups or between fetal and adult male gonads, many genes important for spermatogenesis have been discovered. Genes that are critical at particular stages of spermatogenesis were defined and can be considered as potential male fertility biomarkers. The studies described showed that microarrays may be potentially used as a diagnostic platform to increase the efficacy of diagnosis and perhaps treatment of infertile males.

Evidence for an adaptation in ROS scavenging systems in human testicular peritubular cells from infertility patients

Fibrosis, increased amounts of immune cells and expression of COX-2 in the testes of infertility patients provide circumstantial evidence for a specific testicular milieu, in which reactive oxygen species (ROS) could be increased. If ROS level increase and/or ROS scavengers decrease, the resulting testicular oxidative stress may contribute to human male infertility. Primary peritubular cells of the human testis, from men with normal spermatogenesis (HTPCs) and infertile patients (HTPC-Fs), previously allowed us to identify an end product of COX-2 action, a prostaglandin derivative (15dPGJ2), which acts via ROS to alter the phenotype of peritubular cells, at least in vitro. Using testicular biopsies we now found 15dPGJ2 in patients and hence we started exploring the ROS scavenger systems of the human testis. This system includes catalase, DJ-1, peroxiredoxin 1, SOD 1 and 2, glutathione-S-transferase and HMOX-1, which were identified by RT-PCR/sequencing in HTPCs and HTPC-Fs and whole testes. Catalase, DJ-1, peroxiredoxin 1 and SOD 2 were also detected by Western blots and in part by immunohistochemistry in testicular samples. Western blots of cultured cells further revealed that catalase levels, but not peroxiredoxin 1, SOD 2 or DJ-1 levels, are significantly higher in HTPC-Fs than in HTPCs. This particular difference is correlated with the improved ability of HTPC-Fs to handle ROS, which became evident when cells were exposed to 100 μm H(2)O(2). H(2)O(2) induced stronger responses in HTPCs than in HTPC-Fs, which correlates with the lower level of the H(2)O(2)-degrading defence enzyme catalase in HTPCs. The results provide evidence for an adaptation to elevated ROS levels, which must have occurred in vivo and which persist in vitro in HTPC-Fs. Thus, in infertile men with impaired spermatogenesis elevated ROS levels likely exist, at least in the tubular wall.

A genome-wide association study reveals that variants within the HLA region are associated with risk for nonobstructive azoospermia

A genome-wide association study of Han Chinese subjects was conducted to identify genetic susceptibility loci for nonobstructive azoospermia (NOA). In the discovery stage, 802 azoospermia cases and 1,863 controls were screened for genetic variants in the genome. Promising SNPs were subsequently confirmed in two independent sets of subjects: 818 azoospermia cases and 1,755 controls from northern China, and 606 azoospermia cases and 958 controls from central and southern China. We detected variants at human leukocyte antigen (HLA) regions that were independently associated with NOA (HLA-DRA, rs3129878, p(combine) = 3.70 × 10(-16), odds ratio [OR] = 1.37; C6orf10 and BTNL2, rs498422, p(combine) = 2.43 × 10(-12), OR = 1.42). These findings provide additional insight into the pathogenesis of NOA.

Differential marker protein expression specifies rarefaction zone-containing human Adark spermatogonia

It is unclear whether the distinct nuclear morphologies of human Adark(Ad) and Apale(Ap) spermatogonia are manifestations of different stages of germ cell development or phases of the mitotic cycle, or whether they may reflect still unknown molecular differences. According to the classical description by Clermont, human dark type A spermatogonium (Ad) may contain one, sometimes two or three nuclear ‘vacuolar spaces’ representing chromatin rarefaction zones. These structures were readily discerned in paraffin sections of human testis tissue during immunohistochemical and immunofluorescence analyses and thus represented robust morphological markers for our study. While a majority of the marker proteins tested did not discriminate between spermatogonia with and without chromatin rarefaction zones, doublesex- and mab-3-related transcription factor (DMRT1), tyrosine kinase receptor c-Kit/CD117 (KIT) and proliferation-associated antigen Ki-67 (KI-67) appeared to be restricted to subtypes which lacked the rarefaction zones. Conversely, exosome component 10 (EXOSC10) was found to accumulate within the rarefaction zones, which points to a possible role of this nuclear domain in RNA processing.

Microarray analysis in gynaecology and its findings: a systematic review

Microarray technology is a promising method for investigating gynaecological benign pathology. This systematic review examined various parameters of the design of these studies, the methods used and the gene outcome in these diseases. Electronic searches were performed in Medline (up to April 2009). An overall representation of important genes for each disease detected was performed. The results showed genes were up-regulated or down-regulated. However, studies suffer from several flaws in their design, the sample size employed and the reporting method. In conclusion, a significant amount of work has been performed on benign gynaecological diseases using microarray technology. New trial designs need to be employed that incorporate microarray reporting standards. New research directions should evolve based on these results.

Toll-like receptors and signalling in spermatogenesis and testicular responses to inflammation--a perspective

It is self-evident that infection and inflammation in the reproductive tract can inhibit male fertility, but the observation that fertility may also be compromised by systemic inflammation and disease is more difficult to explain. Recent studies implicating microbial pattern-recognition receptors, such as the Toll-like receptors (TLRs), as well as inflammatory cytokines and their signalling pathways, in testicular function have cast new light on this mysterious link between infection/inflammation and testicular dysfunction. It is increasingly evident that signalling pathways normally involved in controlling inflammation play fundamental roles in regulating Sertoli cell activity and responses to reproductive hormones, in addition to promoting immune responses within the testis. Many of the negative effects of inflammation on spermatogenesis may be attributed to elevated production of inflammation-related gene products within the circulation and the testis, which subsequently exert disruptive effects on spermatogenic cell development and survival, as well as the ability of the Sertoli cells to provide support for spermatogenesis. These interactions have important implications for testicular dysfunction and disease, and may eventually provide new opportunities for therapeutic interventions.

Profiling spermatogenic failure in adult testes bearing Sox9-deficient Sertoli cells identifies genes involved in feminization, inflammation and stress

BACKGROUND

Sox9 (Sry box containing gene 9) is a DNA-binding transcription factor involved in chondrocyte development and sex determination. The protein's absence in testicular Sertoli nurse cells has been shown to disrupt testicular function in adults but little is known at the genome-wide level about molecular events concomitant with testicular break-down.

METHODS

To determine the genome-wide effect on mRNA concentrations triggered by the absence of Sox9 in Sertoli cells we analysed adult testicular tissue from wild-type versus mutant mice with high-density oligonucleotide microarrays and integrated the output of this experiment with regulatory motif predictions and protein-protein network data.

RESULTS

We report the genome-wide mRNA signature of adult testes lacking Sox9 in Sertoli cells before and after the onset of late spermatogenic failure as compared to fertile controls. The GeneChip data integrated with evolutionarily conserved Sox9 DNA binding motifs and regulatory network data identified genes involved in feminization, stress response and inflammation.

CONCLUSIONS

Our results extend previous observations that genes required for female gonadogenesis are up-regulated in the absence of Sox9 in fetal Sertoli cells to the adult stage. Importantly, we identify gene networks involved in immunological processes and stress response which is reminiscent of a phenomenon occurring in a sub-group of infertile men. This suggests mice lacking Sox9 in their Sertoli cells to be a potentially useful model for adult human testicular failure.